Re: vhost + multiqueue + RSS question.

[Gleb Natapov <gleb@cloudius-systems.com>]

On Mon, Nov 17, 2014 at 01:30:06PM +0800, Jason Wang wrote:
> On 11/17/2014 02:56 AM, Michael S. Tsirkin wrote:
> > On Sun, Nov 16, 2014 at 06:18:18PM +0200, Gleb Natapov wrote:
> >> Hi Michael,
> >>
> >>  I am playing with vhost multiqueue capability and have a question about
> >> vhost multiqueue and RSS (receive side steering). My setup has Mellanox
> >> ConnectX-3 NIC which supports multiqueue and RSS. Network related
> >> parameters for qemu are:
> >>
> >>    -netdev tap,id=hn0,script=qemu-ifup.sh,vhost=on,queues=4
> >>    -device virtio-net-pci,netdev=hn0,id=nic1,mq=on,vectors=10
> >>
> >> In a guest I ran "ethtool -L eth0 combined 4" to enable multiqueue.
> >>
> >> I am running one tcp stream into the guest using iperf. Since there is
> >> only one tcp stream I expect it to be handled by one queue only but
> >> this seams to be not the case. ethtool -S on a host shows that the
> >> stream is handled by one queue in the NIC, just like I would expect,
> >> but in a guest all 4 virtio-input interrupt are incremented. Am I
> >> missing any configuration?
> > I don't see anything obviously wrong with what you describe.
> > Maybe, somehow, same irqfd got bound to multiple MSI vectors?
> > To see, can you try dumping struct kvm_irqfd that's passed to kvm?
> >
> >
> >> --
> >> 			Gleb.
> 
> This sounds like a regression, which kernel/qemu version did you use?
Sorry, should have mentioned it from the start. Host is a fedora 20 with
kernel 3.16.6-200.fc20.x86_64 and qemu-system-x86-1.6.2-9.fc20.x86_64.
Guest is also fedora 20 but with an older kernel 3.11.10-301.

--
			Gleb.